NL1024970C2 - Volumetric CT system and method that use multiple detector panels. - Google Patents

Description

Brief indication: Volumetric CT system and method that use more detector panels.

The invention relates generally to the field of non-invasive imaging and, more particularly, to the field of medical imaging using computerized tomography systems.

Computer tomography (CT) imaging systems measure the attenuation of x-ray beams that have passed through a patient from numerous angles. On the basis of these measurements, a computer is able to reconstruct images of the parts of a patient's body that are responsible for the radiation attenuation. As will be apparent to those skilled in the art, these images are based on separate examination of a series of projection images that are moved over an angle. It should be noted that a CT system produces data, which data represents the line integral of linear attenuation coefficients of the scanned object.

This data is then reconstructed to produce an image, which image is typically displayed on a cathode ray tube, and can be printed or reproduced on film. A virtual 3-D image can also be produced by means of a CT examination.

CT scanners operate by projecting fan-shaped or conical X-ray beams from a collimated X-ray source that pass through the object, such as a patient, and are subsequently detected by a series of detector elements. The detector element produces a signal based on the attenuation of the X-ray beams and the data is processed to produce signals, which signals represent the line integrals of the attenuation coefficients of the object along the beam paths. These signals are typically called projections. Using reconstruction techniques, such as filtered back projection, useful images are formulated from the projections. The locations of pathologies can then be located automatically, such as a computer-assisted diagnosis (CAD) algorithm or more conventionally by a trained radiologist.

However, CT detectors cannot provide sufficient resolution to accurately decompose structures in the order of 0.5 to 1.5 mm, which structures may be of diagnostic and pathological interest. . This lack of resolution can be problematic in applications where a larger resolution is desired, such as imaging of the inner ear, imaging of the heart and vascular system, imaging of small animals, and oncological examination.

Moreover, it is often desirable to image large volumes within the body while maintaining a desired X-ray dose. For example, in CT imaging of the heart, it is generally desirable to capture the entire heart on one rotation of the I scanner. Similarly, in perfusion determination of an entire organ, it is generally desirable to capture the entire organ within a single rotation. However, other imaging applications may not require such an extensive field of view and there may occur scanning speed advantages associated with a smaller field of view. It may therefore be advantageous to be able to vary the field of view, which balances the desired field of view with the desired scanning speed. It may therefore be desirable to provide a high resolution in conjunction with a configurable field of view.

The invention provides a means for increasing the available field of view of an imaging system, while in addition increasing the available resolution of the imaging system. In particular, an imaging system is provided in which the detector comprises two or more flat panel X-ray detectors, which are generally positioned adjacent to each other. The field of view enclosed by the two or more flat panels is configurable such that the field of view, the scanning time and the scanning resolution H 30 can be optimized in accordance with the scanning application.

H According to an embodiment of the present technique, an H method is provided for non-invasive acquisition of an image, H which is representative of the internal characteristics of a target. An X-ray beam is emitted by an X-ray source in such a way that at least a part of the X-ray beam passes through a target. The portion of the X-ray beam is detected on a detector. The detector comprises two or more flat-panel X-ray detectors, which generate two or more signals responsive to the portion of the X-ray beam within an arbitrary field of view. The random field of view is defined within an area enclosed by the two or more flat-panel X-ray radiation detectors. The two or more signals within the arbitrary field of view are acquired and processed to reconstruct an image representative of the internal characteristics of the target.

According to another aspect of the invention, a concrete medium for generating an image representative of the internal features of a target is provided. The concrete medium contains a routine for acquiring two or more signals within any field of view defined within an area enclosed by two or more flat panel X-ray detectors. Moreover, the concrete medium includes a routine for processing two or more signals from the random field of view to reconstruct an image representative of the internal characteristics of a target.

According to an additional aspect of the invention, an imaging system is provided. The imaging system includes an X-ray source, which is arranged to emit a beam of X-rays to a target to be imaged, and a detector, which is arranged to detect the beam of X-rays and two or more signals in response to the bundle of x-rays. The detector comprises two or more flat panel X-ray detectors, which enclose a configurable field of view. The imaging system also includes an X-ray controller adapted to control the X-ray source and data acquisition circuitry adapted to receive the two or more signals from the detector. In addition, the system includes a computer adapted to receive the two or more signals from at least one of the data processing circuits and memory circuits and to display an image representative of the internal characteristics of the target to be displayed. reconstruct. Moreover, an operator workstation that is arranged to send one or more commands to at least one of the computer, the data acquisition circuits and the X-ray control is included.

According to another aspect of the invention, an imaging system is provided. The imaging system comprises an X-ray source, which is arranged to transfer a bundle of X-rays to an X-ray beam.

I - 4 - I

emit a target to be imaged, and a detector that is inserted

I aim to detect the X-ray beam and to detect two or more I

I generate signals in response to the X-ray beam. The I

The detector comprises two or more flat-panel X-ray detectors. I

The imaging system also includes an X-ray control, which I

I is arranged to control the X-ray source, and data transfer

recruitment circuits arranged to receive the two or more signals I

from the detector. In addition, the system contains a computer

Iter, which is arranged to receive the two or more signals of at least one I

10 of the data acquisition circuits and memory circuits

I and an image representative of the internal knowledge

Reconstructing marks of the purpose to be imaged. In addition, an I

I operator workstation included, which operator workstation is set up I

I to send one or more commands to at least one of the computer, the ge

15 data acquisition circuits and the X-ray control

I den. The system also includes means for forming one through the I

two or more flat panel X-ray detectors enclosed randomly

I rigid field of vision. I

The foregoing and other advantages and features of the invention

The thing will become clear after reading the following detail

I learned description with reference to the drawings, in which: I

Fig. 1 is a schematic view of an example of an I

I imaging system in the form of a CT imaging system for I

I use in producing edited images according to aspects of I

25 is the invention; I

Fig. 2 shows another schematic view of a physical embodiment

ring of the CT system of FIG. 1; I

Fig. 3 is a schematic view of the detector configuration of I

1 and 2, as seen through the opening of the portal; I

Fig. 4 is a schematic view of the detector configuration of I

Figs. 1 and 2, viewed from the opening side; and I

Fig. 5 is a schematic view of the detector configuration of I

1 and 2 is, as seen from a three-dimensional perspective. I

FIG. 1 schematically shows an imaging system 10 I

I 35 for acquiring and processing image data. In the displayed I

embodiment, the system 10 is a computed tomography (CT) system, I

I designed to acquire original image data and to I

edit the image data for display and analysis according to the above

This technique. In the embodiment shown in FIG. 1, I

The imaging system 10 is a source of X-ray radiation 12, which source is positioned adjacent to a collimator 14. In this preferred embodiment, the source of X-ray radiation 12 is typically an X-ray tube. The collimator 14 allows a stream of radiation 16 to enter an area in which an object, such as a human patient 18, is positioned.

A portion of the radiation 20 passes through or around the object and hits a detector, which is generally designated by the reference numeral 22. Elements of the detector 22 produce electrical signals, which represent the intensity of the incident X-ray beam. These signals are acquired and processed to reconstruct an image of the characteristics within the object.

The source 12 is controlled by a system controller 24, which controller supplies both energy and control signals for CT examination sequences 15. In addition, the detector 22 is coupled to the system controller 24, which instructs acquisition of the signals generated in the detector 22. The system controller 24 can also perform various signal processing and filtering functions, such as initial adjustment of dynamic ranges, interleaving of digital image data, etc. In general, the system controller 24 instructs the imaging system to execute survey protocols and to process acquired data. In the present context, the system controller 24 also includes signal processing circuits, which are typically based on a general-purpose or specific-purpose digital computer, associated memory circuits for storing computer-run programs and routines, as well as configuration parameters and image data, link circuits, etc. .

In the embodiment shown in Fig. 1, the system controller 24 is connected to a rotation subsystem 26 and a linear positioning subsystem 28. The rotation subsystem 26 allows the X-ray source 12, the collimator 14 and the detector 22 to rotate one or more times. the patient 18 can be rotated. It should be noted that the rotation subsystem 26 may include a portal. The system controller 24 can therefore be used to control the portal. The linear positioning subsystem 28 allows the patient 18, or more specifically a patient table or platform, to be displaced linearly. The patient table can therefore be moved linearly within the portal to generate images of particular areas of the patient 18.

1024970-

I -6 - I

As will be apparent to those skilled in the art, the radiation source I

I can also be controlled by an X-ray controller 30 in the I

I system control 24. In particular, the X-ray control system is I

Arranged to transfer energy and timing signals to the X-ray

Source 12. A motor controller 32 can be used I

about the movement of the rotation subsystem 26 and the linear position I

Control subsystem 28. I

The system controller 24 also contains a data processing

Delivery system 34. In this preferred embodiment, the detector 22 is I

I 10 connected to system controller 24 and more particularly to I

I the data acquisition system 34. The data acquisition system 34 I

I receives collected I from the detector 22 by readout electronics

I data. The data acquisition system 34 typically receives from the DE

Detector 22 sampled analog signals and sets the data I

To digital signals for subsequent processing by a computer

Ib 36. I

The computer 36 is typically connected to the system controller 24. I

The data collected by the data acquisition system 34 can be I

I are sent to the computer 36 and moreover to a memory 38. I

It will be appreciated that any type of memory for storing an I

Large amount of data through such an exemplary system 10 can I

I are used. The computer 36 is furthermore arranged to be connected via a computer

I service workstation 40, which is typically equipped with a keyboard and I

other input devices, commands and scanning parameters of a file

I receive the servant. An operator can control the system 10 via the input I

I driving directions. The operator can therefore use the reconstructed I

I image and other data relevant to the system on the computer 36 I

I perceive, initiate imaging, etc. I

A display 42 connected to the operator workstation 40 can I

I 30 are used to observe the reconstructed image and to I

to control imaging. In addition, the scanned image can be displayed on a scan

Printing device 43, which printing device can be printed with the computer

Computer 36 and the operator workstation 40 may be connected. Furthermore, I

The operator workstation 40 also has an image archiving and communication

I 35 cation system (PACS) 44 are connected. It should be noted, I

I that PACS 44 with a remote system 46, an information system of I

I a radiology department (RIS), a hospital information system

I (HIS) or can be connected to an internal or external network, so that I

I 1024970- 7 - others in different locations can access the image and the image data.

It should further be noted that the computer 36 and the operator workstation 40 are connected to other output devices, which may include computer monitors and associated processing circuits of standard type or for special purposes. One or more operator workstations 40 may be included in the system for issuing system parameters, requesting examinations, viewing images, etc. In general, displays, printing devices, workstations and similar devices provided within the system 10 may be located close to the data acquisition components. be or may be remote from these components, such as somewhere else within an institution or hospital, or at a completely different location, and connected to the imaging system via one or more configurable networks, such as the internet, virtual private networks, etc. .

Referring generally to Fig. 2, an example of an imaging system used in a present embodiment may be a CT scanning system 50. The CT scanning system 50 is shown with a frame 52 and a gantry 54, which has an opening 56. The aperture 56 can typically have a diameter of 50 cm. Furthermore, a patient table 58 positioned in the opening 56 of the frame 52 and the portal 54 is shown. The patient table 58 is arranged such that a patient 18 can lie comfortably on his back during the examination process. The patient table 58 is furthermore arranged to be linearly displaced by means of the linear positioning subsystem 28 (see Fig. 1). The portal 54 is shown with the radiation source 12, typically an X-ray tube, which emits X-rays from a focal point 62. The flow of radiation is directed to a certain area of the patient 18. It should be noted that the particular area of the patient 18 is typically selected by an operator such that the most useful scan of an area can be imaged.

In a typical operation, the X-ray source 12 projects an X-ray beam from the focal point 62 to the detector 22. The detector 22 is generally formed by a number of detector elements, which pass through and around an object of interest, such as in particular body parts, for example the liver, pancreas, etc., detecting outgoing X-rays. Each detector element 1024970 -: - I - 8 - I produces an electrical signal that represents the intensity of the X-ray beam at the position of the element at the moment the beam strikes the detector.

The portal 54 is rotated around the object of interest, so that a number of radiographic views can be collected by the computer 36. Thus, an image or slice is acquired which in certain modes may comprise less or more than 360 ° of projection data to formulate an image. The image is collimated to a desired thickness, typically less than 40 mm using lead shutters for the X-ray source 12 and different apertures for the detector 22. The collimator 14 (see Fig. 1) typically defines the size and shape of the x-ray beam that exits from the x-ray source 12.

Therefore, when the X-ray source 12 and the detector 22 rotate, the detector 22 collects data from the attenuated X-ray beams. Data collected by the detector 22 then undergoes a pre-processing and calibration to condition the data to represent the line integrals of the attenuation coefficients of the scanned objects. The processed data, commonly referred to as projections, is then filtered and projected back to formulate an image of the scanned area. As mentioned above, the computer 36 is typically used to control the entire CT system 10. The main computer, which controls the operation of the system, can be adapted to control features made possible by the system controller. Furthermore, the operator workstation 40 is connected to the computer 36 as well as to a display so that the reconstructed image can be viewed.

Once reconstructed, the image produced by the system of Figs. 1 I and 2 reveals internal characteristics of a patient. As is generally shown in FIG. 2, the image 64 can be displayed to show these features, as indicated by reference numeral 66 in FIG. In a traditional approach to

I diagnosis of medical conditions, such as conditions of illness and I

more particularly medical events, a radiologist or I

I consider a copy of the display of the image 64 to be a doctor

I can distinguish characteristic features that are long. Such I

I characteristics may include injuries, extent, and forms of certain anato I

IMS or organs and other features that can be distinguished in the image

Iden are based on the experience and knowledge of the individual physician I

I 1024970- 9. Other analyzes can be based on capacities of different CAD algorithms. Subsequent processing and data acquisition then takes place entirely at the physician's discretion and is based on the physician's expertise.

However, the diagnostic value of the reconstructed image 64 may be limited for various reasons. For example, the X-ray detectors used in CT scanners are typically arranged as a linear array consisting of one or more rows of detector elements. For example, four or eight rows of detector elements may be present in multi-slice CT scanners, while a single row is present in a single-slice CT scanner. The limited number of rows of detector elements, even in multi-slice systems, provides a coverage area along the axis of the patient, ie, a coverage area in the Z direction, which may be insufficient for certain CT-15 imaging applications at a desired x-ray dose. For example, imaging of the heart and total organ perfusion can take advantage of a larger coverage area along the patient's axis, which would allow the acquisition of image data for the entire organ within a single rotation.

Moreover, each row may contain approximately 1000 detector elements, which elements are often referred to as pixels, which elements have a pixel pitch of approximately 1 mm. This pixel pitch provides sufficient resolution to detect anatomical features on the order of 1-2 mm in diameter after post-processing of the acquired image data. However, certain imaging applications, such as imaging of the inner ear, imaging of the heart and vascular system, imaging of small animals and oncological examination, may benefit from a larger CT image resolution. In particular, these types of applications can be improved by being able to reliably distinguish structures with dimensions smaller than the above-mentioned 1-2 mm.

One way that can be used to increase the available field of view, both in the scanning plane and along the axis of the patient, and the image resolution is to form the detector 22 from two or more flat panel 35 x-ray detectors 68 as is 1 and 2. The flat panels 68 have a large isotropic resolution as well as a large field of view. The flat panels 68 may be based on the amorphous silicon technology found in digital X-rays used in medical imaging. 1024970 *

I - 10 - I

Ielling imaging systems. These flat panels 68 can consist of I

I large, monolithic series of photolithographically created high I

I density photodiodes, which are connected to a continuous X-ray

Lint scintillator. When the scintillator by X-rays, such as I

If the X-ray beam 16 or 20 is hit, the signal is generated

Illuminator visible light, which can be detected by the photodiodes

Pine tree. The photo diodes are in turn connected to data processing

Circuitry, which measure and record these signals. The photo slide

I depitch can be around 200 microns, which is a resolution of I

I structures between 0.2-0.4 mm in diameter after finishing the processing

Ive image data provided. I

The panels 68 can generally be adjacent to each other and I

I placed tangentially to the circular arc of the portal I

I are. By placing the surface I as tiles together

I 15 panel detectors 68, can be a field of view large enough to accommodate the I

I to accommodate clinical scanning of humans or large animals, I

I be created. Although it is shown in FIG. 2 that the flat panel sectional I

If the detectors 68 are placed in a straight line, the panels 68 may

I are also arranged in a stepped manner, i.e. such that the edge I

Are not accurately aligned, or by other means that are suitable

I can be for different scanning techniques, such as spiral I

I scans. I

The increase provided by the use of flat panels 68

However, a field of view along the axis of the patient can be used for many

I adjustments are undesirable. In applications where the magnified I

I, the field of view is undesirable, the area with the larger field of view I

The associated extended scanning time may be undesirable. For example in an output I

I embodiment, in which the detector 22 comprises two 20 cm digital flat panels

I 68 with a natural frame rate of 30 Hz can hold 900 vol

I 30 empty-panel projection views are provided in about 30 seconds

I worven. however, if the data readout is limited to. the central I

I 360 rows of the panel, 1000 panel views in about I

8 seconds are obtained. I

It may therefore be desirable to have an arbitrary field of vision

35, which field of view can be formed by an operator

So that the volume enclosed by the field of view and the scanning time I

optimized based on the imaging application. It wants I

Any field of vision can be determined by forming one of I

both or both of the in-plane field of view, determined by the number of I

Detector panels used in the system, and the field of view along the axis of the patient, i.e., the coverage area in the Z direction, determined by the number of read rows of each panel. Changing each of these parameters will affect the amount of data read out by the system.

Referring to FIG. 3, the flat panels 68 may, for example, strongly enclose one dimension defined by the arc 70, which arc defines the in-plane field of view, with only end portions 72 of the detector 22 extending beyond the acquisition circuitry. 34 selected area. However, along a second dimension, the field of view read out by the data acquisition circuit 34 may be reduced along the axis of the patient, whereby the total amount of acquired image data is reduced and image acquisition can occur faster, as shown in FIG. 4. This is shown in FIG. Figure 4 is shown as limiting data acquisition to the central area 74 of a flat panel 68, leaving end areas 76 unread, i.e., limiting the coverage area in the Z direction. A three-dimensional representation of an arbitrary field of view, generally according to the configuration shown in FIGS. 3 and 4, is provided by FIG.

Other options are of course possible, depending on the desired field of view and the desired scanning speed. For example, the field of view dimension shown as an arc 70 in FIG. 3 may be reduced instead or the extent of the area 74 read in the dimension shown in FIG. 4 may be increased or decreased to adjust the displayed volume and associated scanning time. to suit. Similarly, it is not necessary for all panels 68 of the detector 22 to be read in an identical manner, but instead, the surface of each panel 68 that is being read can vary to allow for different scanning techniques, such as spiral scanning processing. to accommodate.

Readout can be effected within panels 68 by joining two or more adjacent rows or columns to shorten the data acquisition time at the expense of image resolution. In this embodiment, image resolution and non-image volume can be sacrificed to reduce the scanning time. Similarly, photodiodes within the flat panels 68 can be selectively read out to create a conventional or random field of view within the area enclosed by the flat panels 68 as determined by the operator and the application.

Although the invention may be susceptible to numerous modifications and alternative forms, specific embodiments are only shown by way of example in the drawings and described in detail herein. It will be understood, however, that the invention is not intended to be limited to the particular forms disclosed. The techniques explained herein may be applicable to non-medical imaging applications, such as parcel and baggage check and other forms of security check and non-invasive check, where the interior of an object to be imaged has to be visualized. The invention, on the other hand, aims to cover all modifications, equivalents, and alternatives that fall within the spirit and scope of the invention, as defined by the following appended claims.

I 1024970

Claims (13)

A method for non-invasively acquiring an image representative of the internal characteristics of a target, comprising: transmitting from an x-ray source (12) an x-ray beam (16) such that at least a portion (20) the x-ray beam (16) passes through the target; detecting at least the portion (20) of the x-ray beam (16) on a detector (22) that includes two or more flat-panel x-ray detectors (68), said detectors (68) two or more on the portion (20) generate signals responsive to the X-ray beam (16) within a random field of view, the random field of view being defined within an area enclosed by the two or more flat panel X-ray detectors (68); acquiring the two or more signals within the random field of view; and processing the two or more signals from the random field of view to reconstruct an image (64) representative of the internal features (66) of the target. A method according to claim 1, wherein acquiring the two or more signals within the random field of view comprises acquiring two or more signals detected by a central region (74) over the two or more flat panel X-ray detectors. 3. A method according to claim 1 or 2, wherein acquiring the two or more signals within the random field of view comprises selectively reading out two or more rows of photodiodes from the two or more flat panel X-ray detectors (68), the photo diodes to be read are selected by at least one of an operator and a computer algorithm. The method of claim 3, wherein the photo diodes to be read out are selected such that the random field of view and a scanning time are optimized for an imaging application. 5. A method according to claim 3, wherein the photo diodes to be read out are selected such that the random field of view, a scanning time and an image resolution are optimized for an imaging application. 1024970- I - 14 - An imaging system (10) capable of generating images representative of the internal characteristics of an imaging target, comprising: an X-ray source (12) arranged around a beam I ( 16) to transmit from x-rays to an imaging target; I a detector (22) adapted to detect the X-ray beam (16) and to generate two or more signals in response to the X-ray beam (16), the detector (22) having two or more flat panel x-ray detectors (68) that encloses a configurable field of view; An X-ray controller (30) adapted to control the X-ray source (12); data acquisition circuits (34) adapted to receive two or more signals from the detector (22); A computer (36) adapted to receive the two or more signals from at least one of the data acquisition circuits (34) and memory circuits (38) and an image (64) I representative of reconstruct the internal features (66) of the imaging target; and an operator workstation (40) adapted to send one or more I commands to at least one of the computer (36), the data acquisition circuits (34) and the X-ray controller (30). The imaging system (10) according to claim 6, further comprising: a portal (54), in which the x-ray source (12) and the detector (22) are included; A platform (58) adapted to be positioned in the portal (54); A rotation subsystem (28) adapted to rotate the portal I (54); and a linear positioning subsystem (28) adapted to position the platform (58) in the portal (54). I An imaging system (10) according to claim 6 or 7, wherein the configurable field of view has a magnitude in accordance with one or more of at least one of the parameters (received from the computer (36) and the operating terminal (40)). I I 1024970- 15 The imaging system (10) of claims 6-8, wherein the configurable field of view is formed based on a desired field of view and a desired scanning time. The imaging system (10) of claim 9, wherein one or more of at least one acquisition commands received from the operator workstation (40) and the computer (36) determine the desired field of view. The imaging system (10) according to any of claims 6-10, wherein the configurable field of view is formed based on a desired field of view, a desired scanning time and a desired image resolution. The imaging system (10) of claim 11, wherein one or more acquisition commands received from the operator workstation (40) and the computer (36) determine the desired field of view. The imaging system (10) according to any of claims 6-12, wherein the imaging system (10) is a CT imaging system. 1024970 *